Tracers can include chemicals or other substances that are leached out by wellbore fluids over time in a wellbore. The tracer chemicals or substances can be detected in fluid produced from the wellbore at the surface for, among other things, determining the zone that is producing the fluid. Retaining tracers in a zone, or with respect to a screen joint in a zone, can be challenging. In most screen joints the fluid produced (or injected) through the joint passes through openings in the base pipe of that joint, and tracers can be easily contained within an annular space between the filter media of the joint and the base pipe of the joint by closing the annular space at each axial end of the joint. In some screen variations, however, the annular space between the filter media and the base pipe is connected across multiple screen joints, and the fluid produced (or injected) through the joints must pass through the annular space to a relatively few flow controlled openings located within special screen joints or between screen joints. In these screen variations, it is desirable to retain the tracers in a fixed position within each screen joint so that the tracers cannot move along the annular space when fluid is flowing in the annular space.